Spine-tailed sea snake description

The spine-tailed sea snake (Aipysurus eydouxii) is also known as Eydoux’ sea snake (1), and is named after Joseph Eydoux, a French naturalist in the 1800s (5).

Like other sea snake species, the spine-tailed sea snake has a flattened, paddle-like tail which enables it to swim efficiently, and its nostrils are positioned higher up on its head than in terrestrial snakes, which makes it easier for this marine reptile to breathe when it surfaces (6). The scales on the top of the spine-tailed sea snake’s head are large and symmetrical (2)(3)(7), and the body scales are smooth, except for those on the underside of the midsection, which are weakly keeled(2).

The background colour of the spine-tailed sea snake is usually cream or salmon to brownish or olive-green above (2)(8), often becoming paler on the underside (8). Many of the scales have dark edges (2)(8), and the skin is patterned with irregular, incomplete dark bands, which often taper on the flanks (2).

The spine-tailed sea snake has 8 to 12 very small teeth located behind its venom fangs (3)(8), which are much smaller than the fangs of other sea snake species (9)(10).

Related species

Spine-tailed sea snake biology

While some sea snake species eat a wide variety of prey, the spine-tailed sea snake has an extremely specialised diet (7), feeding exclusively on fish eggs (2)(3)(4)(7)(9)(10).

As it does not need to immobilise large, moving prey, the spine-tailed sea snake’s fangs are greatly reduced in size and its venom glands, although functional, are rather small (9)(10). The spine-tailed sea snake’s venom is approximately 40 to 100 times less toxic than that of other sea snake species (10). It is also reluctant to bite, so it is not considered to be dangerous to humans (2).

Species within the Aipysurusgenus spend all their lives in the water, never venturing onto land (9). Despite being an air-breathing animal, the spine-tailed sea snake is capable of remaining underwater for up to two hours at a time, before surfacing to breathe again. Its single, elongated lung, which extends for almost the entire length of its body, is highly efficient for gas exchange, and sea snakes are also able to absorb oxygen through their skin when underwater. As in other sea snake species, the spine-tailed sea snake has specialised valves which block off the nostrils while underwater (12).

Living in the marine environment poses several challenges, and as in other sea snake species, the spine-tailed sea snake has a specialised gland under its tongue which enables it to excrete excess salt from its body. Additionally, other marine species such as algae and barnacles often become attached to the sea snake’s skin, a problem which is solved each time the skin is shed, which usually happens once every two to six weeks (12).

Like most species of sea snake, the spine-tailed sea snake is viviparous, meaning that it gives birth to live young rather than laying eggs (4)(12). Mating in sea snakes is a lengthy affair, and the males are unable to disengage from the female until copulation is complete (12). There is little information available on the specific breeding biology of the spine-tailed sea snake (4), but in northern Australia the gestation period is thought to be around six to seven months, with the females giving birth in September, and reproducing every year (12). An average of 4 young are thought to be produced per clutch (4)(12), but in Queensland the spine-tailed sea snake is known to give birth to up to 12 young (12).

Spine-tailed sea snake range

A widespread but patchily distributed species (1), the spine-tailed sea snake occurs from the northern coast of Australia to Southeast Asia (2)(9). This range includes the coast of Queensland, as well as the Gulf of Thailand, Indonesia, Malaysia, Vietnam, Papua New Guinea, Singapore and New Caledonia (1)(2)(3)(9).

Species with a similar range

Spine-tailed sea snake habitat

The spine-tailed sea snake is unusual among sea snakes in that it does not inhabit clear, coral reef waters (3)(9), instead preferring cloudy waters over a muddy substrate (1)(2)(7). This species is common in river mouths, estuaries and bays (1)(7)(11), and is usually only found in areas of shallow water, up to 50 metres in depth (1)(2)(7).

Spine-tailed sea snake threats

Spine-tailed sea snake conservation

As the spine-tailed sea snake is not currently considered to be at risk of extinction, at present there are no conservation measures in place specifically targeting this species (1). However, to ensure that it does not become threatened in the future, recommendations for the conservation of the spine-tailed sea snake include monitoring bycatch, as well as introducing the use of exclusion devices in fisheries to reduce the levels of bycatch(1).

All sea snake species in Australia are protected under their classification by the Department of Environment and Water Resources as ‘Listed Marine Species’. In addition, sea snakes are protected under the Environment Protection and Biodiversity Conservation Act 1999, while the Australian Fisheries Management Act 1991 requires fisheries to avoid impacting on protected or threatened species, including sea snakes. A three-year study has been instigated to develop and implement a long-term bycatch monitoring programme for Australia’s Northern Prawn Fishery, which has the largest impact of any Commonwealth-managed fishery on protected sea snake populations (1).

Since 2003, industry workshops have been jointly run by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) and Australia’s Fisheries Management Authority (AFMA) to train prawn fishery crew members on how to identify, photograph and record information regarding sea snake capture during the main prawn seasons (1).

Authentication

Glossary

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Bycatch

In the fishing industry, the part of the catch made up of non-target species.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Gestation

The state of being pregnant; the period from conception to birth.

Gland

An organ that makes and secretes substances used by the body.

Keel

A projecting ridge along a flat or curved surface, particularly down the middle.

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